1. Field of the Invention
The present invention relates to a portable timepiece in which there is a possibility of the inner pressure of a timepiece exterior assembly increasing as in the case, for example, of a diver's watch suitable for saturation diving.
2. Description of the Prior Art
There is known a diver's watch for saturation diving in which, in order to cope with a case where the inner pressure of the timepiece exterior case has become higher than the exterior pressure, the gas inside the timepiece exterior case can be forcibly discharged to the exterior of the case by artificially depressing a button of a vent valve provided in this case (See, for example, JP-A-5-172956).
The vent valve with which the diver's watch is equipped with a stepped hole formed in a case band of the timepiece exterior case, a button, a retaining ring, a coil spring, and packing.
A small diameter hole portion of the stepped hole is open to the inner side of the case band, and a large diameter hole portion of the stepped hole is open to the outer side of the case band. The button has an operating portion fit-engaged with the large diameter hole portion, and a shaft portion extending through the small diameter hole portion. The retaining ring, which prevents detachment of the button from the stepped hole, is connected to the shaft portion within the timepiece exterior case. The coil spring is accommodated in the large diameter hole portion while fitted onto the shaft portion, and urges the button toward the exterior of the case band. The packing is fixed to the shaft portion. In the normal state, in which the button is not pushed in, this packing exhibits interference while in contact with the inner surface of the small diameter hole portion or of a pipe fitted into this hole portion, and, in the state in which the button is pushed in, it is arranged inside the case band and exhibits no interference.
Thus, simultaneously with the pushing-in operation of the button, the packing is moved so as to be detached from the small diameter hole portion of the stepped hole to the interior of the case band, and communication is established between the interior and the exterior of the case band via the stepped hole. As a result, it is possible to discharge the gas inside the timepiece exterior case to the exterior of this case via the stepped hole.